The reason I mentioned it is because we've had members ask about leaving the children aboard while the adults went ashore, and they were talking about little kids. I never understood why they'd want to do that.
MSC follows the typical kids programs plan with daytime activities at scheduled times. It wouldn't be an all-day continuous thing, but rather one with set start/stop times such as for lunch, and to give the staff a break and provide time for cleaning of the activity rooms.
A common thing I've heard about MSC is their service is not as anticipatory as you'd find on most other lines, but rather a 'if you want something more than the basics, ask and we'll do it' approach. Some prefer it that way as it is less fawning, but those who like the pampering look at it as poor service. And hence a lot of negative reviews.